The growth of computer networks, both local to one area and among remotely located areas, has spawned increased interest in collaborative computing applications. These applications allow users at multiple computing devices to work together, running the same application and viewing the same data. For example, consider a word-processing collaborative application. Through network connections, a set of users can see and collaboratively edit a document. In another example, a frustrated user shares an application's error logging screen with a remote technical support specialist. The user runs the application while the specialist views the logging screen to discover what causes the application to fail.
In many implementations, the collaborative application actually runs on only one device, called the “application sharer” or the “local device,” and that device shares the collaborative application display with all other devices, called “application viewers” or “remote devices.” On the sharer and on all of the viewers runs a collaborative computing utility program that allows remote users to see the same display created by the collaborative application for the sharer device. An advantage of these implementations is that the application need not be modified to support collaboration. The application may run for the sharer's user and be unaware that its display is shared to remote users.
In many scenarios, it is not enough for all users to be able to see the display produced by the collaborative application for the application sharer's device. Users at the remote devices would like to provide input to the display. Some collaboration systems allow the users to pass control among themselves so that each in turn can run the collaborative application as if it were running on his own device. In another scenario of remote user interaction, the collaborative application presents its display to all connected users. The remote users may not send input to the collaborative application, but they may wish to annotate the collaborative application display in order to call the attention of the other users to a particular point. Rather than relying on the traditional but confusing voice cues “Look, up near the top,” “No, not that line, the one below it,” “It's the, let's see, one, two, three, fourth column from the right,” “I meant the ‘thee,’ not the ‘the’,” some collaborative computing utilities support visual annotation in which users “draw” on the collaborative application display. The users' annotations are not sent as input to the collaborative application, but they are displayed to all users.
In previous annotation systems, each user creates annotation information (which may include a pointer, a highlighted area, etc.) and sends this annotation information to all other users. Each device, including the annotator's, combines the annotation information with the display received from the collaborative application. This method has many shortcomings. First, there is no central control to coordinate the annotations from multiple users or to turn off annotations for a while if that is desired: every user can annotate at any time. The lack of central control also means that there is no guarantee that all users are seeing the same annotations, which can increase confusion in the collaborative effort beyond what it would have been without visual annotation. As the collaborative application is actually running only on the sharer, a remote user's annotations are not tied directly to the current application display, that is, the application may change the display after the remote user annotates it. Finally, the process of receiving annotations from all of the other users and combining that information with the shared display received from the collaborative application may tax the resources of a remote device, especially a lower-power portable or handheld device.
What is needed is an annotation system for collaborative applications that better coordinates the annotation input from all the users while presenting less of a burden to remote devices.